Re: [PATCH] fix qemu build with xen-4.18.0

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Dec 08, 2023 at 10:59:03AM +0000, Peter Maydell wrote:
> On Fri, 8 Dec 2023 at 09:25, Daniel P. Berrangé <berrange@redhat.com> wrote:
> >
> > CC'ing the Xen folks
> >
> > On Thu, Dec 07, 2023 at 11:12:48PM +0000, Michael Young wrote:
> > > diff --git a/include/hw/xen/xen_native.h b/include/hw/xen/xen_native.h
> > > index 6f09c48823..04b1ef4d34 100644
> > > --- a/include/hw/xen/xen_native.h
> > > +++ b/include/hw/xen/xen_native.h
> > > @@ -532,7 +532,7 @@ static inline int xendevicemodel_set_irq_level(xendevicemodel_handle *dmod,
> > >  }
> > >  #endif
> > >
> > > -#if CONFIG_XEN_CTRL_INTERFACE_VERSION <= 41700
> > > +#if CONFIG_XEN_CTRL_INTERFACE_VERSION >= 41700
> >
> > This change is not correct
> >
> > We can see the upstream change was introduced in 4.17:
> >
> >   $ git describe  2128143c114
> >   4.16.0-rc4-967-g2128143c11
> >
> > IOW, if we have 4.17 or newer these constants already
> > exist. If we have 4.16 or older, then we need to define
> > them to provide back compat.
> 
> Wouldn't that suggest we want "< 41700" ? Or did 4.17 have
> some issue that means we need the back-compat there too?

Oh yes, and if we change it from '<=' to '<', then we get the same
build problem for  qemu-system-aarch64 on x86_64 host, when built
against xen-devel 4.17, which is what I'd expect.

So our accident <= instead of < has masked the pre-existing flaw.

With regards,
Daniel
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